Sighting apparatus.



33 -238. mm 1,211,401 SR W. A. BURNS.

SIGHTING APPARATUS.

APPLICATION FILED JULY 31. 1916.

1,211,401 Patented Jan. 9, 1917.

ggl" ha) m 9 UNITED STATES PATENT OFFICE.

WILLIAM ALBERT BURNS, F DRUMMONDHILL, SCOTLAND, ASSIGNOR TO VICKEBS LIMITED, 0]? LONDON, ENGLAND.

SIGHTING APPARATUS.

Specification of Letters Patent.

Patented J an. 9, 1917.

Original application filed October 30, 1915, Serial No. 58,911. Divided and. this application filed July 31, 1916. Serial No. 112,398.

To all whom it may concern.-

Be it known that I, WILLIAM ALBERT BURNS, a subject of the King of Great Britian, residing at Drummondhill, in the county of Inverness, Scotland, have invented certain new and useful Improvements in Sighting Apparatus, of which the following is a specification.

This invention relates to sights of the kind that are termed speed sights, that is to say sights embodying devices such as a crank or equivalent angularly movable member which is adapted to be adjusted as regards its throw in accordance with the speed of the target and as regards its angular position in accordance with the direction of travel of the target, so that the line of sight will be corrected to compensate for deviation of the projectile due to movement of the target during the interval between the firing of the gun and the striking of the target by the projectile. This movement is often known as the travel of the target, and requires travel allowance or travel correction to be applied to the sights.

Projectiles involving travel correction may be divided into two classes, which I may term visible and invisible. The former class comprises all projectiles which may be traced over the whole, or some part, of their flight either owing to their size, their slowness of flight, or their possession of a device which emits a trail of smoke or a flame to mark their path. The invisible class to which the present invention more especially relates, comprises all bullets and projectiles that cannot be seen in flight.

According to the present invention the improved sighting apparatus comprises a foresight or sighting index longltudinally or radially adjustable, in accordance with the speed of the target, on the aforesaid crank or the like adapted to be set to the direction of travel of the target, this direction in the case of a target such as an aeroplane being of course considered as the horizontal component of travel or the direction in plan view.

For convenience in giving orders or instructions or referring generally to the direction of travel of a target, the mode of expression adopted by riflemen in referring to hits on a target may advantageously be used, and the angularly adjustable crank be associated with a circular scale or dial to enable the crank to be set on the clockface principle. For instance, a target traveling from right to left in a direction at right angles to the line of sight is considered a nine-oclock target, and the scale or dial is such that when the crank is set to indicate the same time of day, an angle of sight duly corrected for horizontal direction of travel of the target is established. The crank is conveniently secured to or integral with a disk the periphery of which is marked with twelve successively numbered graduations or hours for cooperating with an arrow or pointer. The sighting index itself is preferably so shaped as to be broad in side elevation and narrow in end elevation so as to serve to indicate to the firer the amount of spread of fire necessary for insuring effective firing at a target or a number of targets varying in speed and traveling in any one of a number of different directions.

In the accompanying drawings :'-Figure 1 illustrates how, in referring to the direction of travel of a target, I adopt the mode of expression used by riflemen in referring to hits on a target. Fig. 2 is a plan; Fig. 3 is a vertical section, and Fig. 4 an elevation (as presented to the firer) of one form of rotary crank foresight mechanism embodying the features of the invention.

Referring first to Fig. 1, a represents an aeroplane as target which is assumed to lie at the center of a clock-face or dial, and to fly toward one of the hours. The dial is so positioned that the line of sight from the firer F R to the; target passes through the six oclock division. Hence a target flying from right to left (as shown in the figure) crossing the firers line of sight at right angles may be called a nine oclock or more shortly a nine target. A six target is one flying directly toward the firer and so on.

Referring now to Figs. 2, 3 and 4., which represent one embodiment of foresight mechanism to which the above described clockface principle is applied as a system of adjustment, D is a crank carrying a sighting index F mounted on a base F so carried by the crank that it can be setto various distances from the center of rotation P of the crank to vary the speed allowance. The

crank arm D may be carried on a suitable turntable D, or the like, provided with a circular scale D divided into twelve parts, numbered from 1 to 12 respectively, corresponding with the hours of direction as in Fig. 1, the arrangement being such that it is only necessary to set the scale say to the nine graduation as shown in Fig. 4, to set the crank to its rotary position for a nine oclock target. The rotation of the turntable and crank may be effected by the layer by any suitable means. In the drawing the means shown consist of a driving spindle R carrying a miter wheel B in gear with a miter wheel B on the stem of the turntable D. The sliding base F may carry any form of foresight, but, where an aperture backsight is employed, it may be preferable to use the form of foresight or sighting index F shown in the figures. The foresight F, which is T-shaped in side elevation, is cut out of sheet metal or otherwise formed, so that when seen in the end-on position (as in Fig. 3) it is quite narrow like a blade sight. The scale shown in Fig. 2 graduated from 0 to 100 is assumed to show the necessary distances measured from the zero point P to which the foresight has to be moved on the crank to be correctly set for targets having speeds up to 100 miles per hour. P at 10 M. P. H., P at 60 M. P. H., and P at M. P. H., may be called selected points. The point P may be assumed to be the correct mean setting for a target composed of a group of aeroplanes, the speeds of which vary between 65 and M. P. H. The cross bar of the T-shaped foresight F may be made wide enough to span the interval between 65 to 95, and thus indicate to the firer to what extent he must spread his fire, to make sure of hitting one or more of the aeroplanes, the speeds of which lie somewhere within the 65 M. P. H. and 95 M. P. H. limits, their line of flight being at right angles to the line of fire. As the targets direction changes, that is to say as its direction becomes more and more parallel to the line of fire, the required amount of lateral spread of fire, so to speak, becomes less and less, until with a six or twelve target no lateral spread is required. Now as the crank is rotated concurrently with such changes of target direction, the width of the cross bar of the foresight appears to be reduced simultaneously, until at six or twelve it is as shown in Fig. 3. Thus the device is automatic in its indication of the amount of spread required. Other points may be selected, such as P for targets lying within 45 M. P. H. and 75 M. P. H. or P for slower targets between 25 M. P. H. and 65 M. P. H. Obviously the selection of these points and the determination of the width of the cross bar of the foresight is purely a matter of choice.

While I have described a form of foresight or sighting index suitable for use with a rotary crank mechanism, the same form may be employed by itself in connection with any suitable form of backsight, provided it is capable of being revolved as required, for the purpose of indicating the amount of spread of fire necessary in the case of targets, the speed of which lies between given limits.

The invention has been described as applied to the firing of stationary ordnance, but it will be understood that it may be adopted also in connection with ordnance mounted 011 moving platforms, such as aircraft, in which case the means above described will be used with or embodied in means for correcting the sights for gun platform speed, as described for example in the specification of my British application for patent No. 18351 of 191&. Also in the case of stationary ordnance employed against aircraft, it will be understood that the mechanism as a whole must be so mounted on the gun that the axis about which the crank turns is kept vertical at all elevations of the gun in accordance with the basic principles of anti-aircraft rotary correcting gear for sighting as disclosed in my prior British Patent N o. 2129 of 1910.

\Vhat I claim and desire to secure by Letters Patent of the United States is 1. In sighting apparatus for use with guns firing at traveling targets, the combination with the sighting index of an angularly displaceable member on which said index is mounted, and means for adjusting said member so that a line joining the sighting index to the axis of movement of the member is parallel to the direction of travel of the targe 2. In sighting apparatus for use with guns firing at traveling targets, the combination with the sighting index, of an angularly displaceable member on which said index is adjustable toward and away from the axis of movement of said member in accordance with the speed of the target, and means for adjusting said member so that a line joining the sighting index to the said axis of movement of the member is parallel to the direction of travel of the target.

3. In sighting apparatus for use with guns firing at traveling targets, the combination with the foresight, of a crank arm, means for mounting said foresight on said crank arm so as to be adjustable longitudinally thereon in accordance with the speed of the target, and means for angularly adjusting said crank arm to correspond in angular position to the direction of travel of the target.

4. In sighting apparatus for use with guns firing at traveling targets, the combination with a support, of an angularly movable sighting index mounted on the support and adapted to be set in angular position in conformity with the direction of travel of the target, said index being so shaped as to indicate, in accordance wlth its angular position, the amount of spread of fire necessary to hit the moving target.

5. In sighting apparatus for use with guns firing at traveling targets, the combination with an angularly movable member adapted to be set in angular position in conformity with the direction of travel of the target, of a sighting index of T shaped formation mounted on said member.

6. In sighting apparatus for use with guns firing att ragehngiargets, the combination with the sighting index, of an angularly movable member carrying said index and adapted to be set in angular position in conformity with the direction of travel of the target, and a scale graduated on the clock face principle for enabling the said member to be readily set to any desired angular position.

7 In sighting apparatus for use with guns firing at traveling targets, the combination with the sighting index, of a crank arm on which the sighting index is slidably carried so that the distance of the index from the crank arm axis can be adjusted in accordance with the speed of the target, means for setting said crank arm so that its angular position agrees with the direction of move ment of the target and a circular scale graduated on the clock face principle for enabling said crank arm to be readily set to any desired angular position.

In testimony whereof, I hereto aflix my signature.

WILLIAM ALBERT BURNS.

copies of this patent may be obtained for five cents each, by addressing the "Commissioner of Patents, Washington, D. 0. 

